Lotus will run its latest Coanda-effect exhaust system at this weekend's United States Grand Prix, but Kimi Raikkonen says the team still needs to work on the car's setup to maximise performance ahead of qualifying.

Lotus's latest exhaust is designed to bring the downforce benefits of its existing Coanda-effect system but without the loss in power. After testing the new version in Abu Dhabi and again on Friday in Austin, the team has confirmed it will run the new design.

However, Raikkonen said a general lack of grip from the circuit means Lotus still has plenty of setup work to do on Saturday ahead of qualifying.

"[The track] improved in the first session and again in the second, but at least for us it is very slippery," he said. "We just tried to get through corners without sliding too much so it's very disappointing. Hopefully we'll find something and get the car working a bit better.

"It doesn't really matter what we did, we just don't have the grip. It's not just the rear end, it's the front end also and we just keep moving the issues whatever we do. We probably just don't really have the grip right now and the tyres are not working for us. Maybe the others have more downforce, but we'll wait and see what happens tomorrow."

However, Raikkonen is not too worried about the lack of grip as he is confident the car will improve ahead of qualifying.

"Our car is not exactly like we hope and I think there are many things to put it together," he said. "The grip on the circuit is the biggest thing, but usually every race we are suffering a bit on the Friday and then once the grip starts to build up we get stronger. Probably we don't have enough downforce, but we know the circuit ad let's just hope we can improve the car for tomorrow."

The International Rugby Board (IRB) have stripped Australia of the right to host a round of the World Sevens Series, scheduled for Brisbane on 16-17 February, after the Australian government's refusal to provide visas for the squad from Fiji